Abstract
LANA, the major latency-associated nuclear antigen of Kaposi's sarcoma herpesvirus/human herpesvirus-8 (KSHV/HHV-8), binds RING3 protein, one of five human homologues of the fsh (female sterile homeotic) gene product of Drosophila. In KSHV/HHV-8-infected cells LANA and the viral episomes accumulate in heterochromatin-associated nuclear bodies. Here we show that in several KSHV/HHV-8-negative cell lines derived from carcinomas, sarcomas and lymphomas, RING3 was expressed at low levels, primarily localized to the euchromatin, and dissociated from the chromosomes during mitosis. In contrast, in KSHV/HHV-8-infected body cavity lymphoma cells the bulk of RING3 localizes to the LANA nuclear bodies and remains associated with the chromosomes during cell division. KSHV/HHV-8-infected body cavity lymphoma cells expressed RING3 at much higher levels than cells without the virus. Transfection of full-length LANA, but not the C terminus alone, greatly induced RING3 gene expression, and LANA and RING3 co-localized even in the transfected cells, in the absence of KSHV/HHV-8 viral DNA. High levels of LANA expression led to the disappearance of heterochromatin in both human and mouse cells. We suggest that LANA and RING3 may create a local euchromatic microenvironment around the viral episomes that are anchored to the heterochromatin.